At theorical perfection, evaporative cooling is an adiabatic process. Incoming air passes through a humidifying medium and evaporates water into the air stream. Water molecules take on heat and achieve the change from a liquid to a gaseous state and sensible heat is converted into latent heat. The process reduces dry bulb temperature over a constant wet bulb temperature. The wet bulb temperature is the limit on direct evaporative cooling. It is the full saturation temperature and is the theoretically coolest to which direct evaporation can reduce the temperature.
Years of research and engineering skill in the art have evolved the conventional square metal evaporative cooler. Automated factories now produce square metal units extremely fast and accurately at a relatively low direct cost. However, while engineers have precisiontuned this art to its apparent ultimate productive capability, there does not appear to have been any practicle, fundamental advances in the design of evaporative coolers.
Conventional evaporative coolers predominantly attempt to use the evaporative process by means of a foursided metal design. Typically, four (three on sidedrafts) removable pad holders contain an evaporating medium (the "pad" ) which is usually made of aspen fibers. The pad holders are provided with a rigid exterior and use wire grids to sandwich the pads to hold them in place. Water distribution is usually accomplished by copper lines feeding a set of distribution troughs or, as in U.S. Pat. 3,867,486, a plurality of fluid supply channels. The units have generally been made of light guage metal, preferably galvanized to reduce rust. Conventionally, the top and bottom are permenantly connected by a set of corner struts which also support the removable pad holders. A forward curved centrifugal blower is generally to draw air through the pads and exhaust it into the area to be cooled.
Annual maintenance required removing all of the pad holders and individually cleaning the pads, in addition to performing a general lubrication of the blower and motor to extend the life of metal parts. It was necessary to clean out rust and scale deposits and then recoat the metal in some manner with a water-proof or corrosion resistant coating.
Major problems in maintaining a high evaporative efficiency have been in keeping the pads sealed and saturated. Open areas allow unsaturated flow as do dry areas. Since these areas offer less resistance to air flow, the velocity of air through them tends to be higher and adjacent saturated areas also become partially dry. Thus a major objective of pad and water distribution design improvement has been to obtain good seals on pads and keep them evenly and well saturated.
Shipping has of necessity been of completely assembled units. The need to secure the top and base together made nestable shipping impractical. Assembly by unskilled persons without highly specialized equipment was considered impossible or economically impracticle and thus it was necessary to ship a large amount of "air" in the assembled units at a cost that became very significant with longer and, especially, overseas shipment.
Although some improvements have been made in square coolers, a small number of prior art round coolers continue to be made and these were beset by difficulties with mass production methods and by metal waste problems. These problems have been overcome by the present invention which provides an evaporative cooler having an even air flow and high saturation efficiency, combined with compact and nestable shipping.
Accordingly, a principal object of this invention is to provide an evaporative cooler having an increased effective pad area capable of being uniformly and more effectively saturated with water. Another object is to provide a pad having no unsealed areas and in which such unsealed areas are eliminated by preventing the wet pad from sagging once it is placed in the cooler. Still another object is to provide for increased pad area by providing a pad having no corners and fewer seams. Yet another object is to provide an evaporative cooler in which the pad is made of a single piece and is capable of rapid changing. Another object is to provide an evaporative cooler in which there is no possibility or danger of water overflowing into the occupied areas below. Still another object is to provide such a cooler which does not require a level surface for operation. A further object is to provide an evaporative cooler which does not require periodic maintenance to remove rust and mineral collections and in which the cooling efficiency is not diminished by parts heated by the sun. Yet a further object is to provide an evaporative cooler which is capable of nestable assembly.
These and other objects which will become apparent to those skilled in the art are achieved in accordance with the present invention as described in the following specification and in the accompanying drawings.